CHECKPOINT THERAPEUTICS, INC. Checkpoint Therapeutics, Inc. announced positive interim efficacy results from its registration-enabling clinical trial evaluating its anti-PD-L1 antibody, cosibelimab, in patients with locally advanced cutaneous squamous cell carcinoma (cSCC) who are not candidates for curative surgery or radiation. The design of the interim analysis incorporated recent feedback from the U.S. Food and Drug Administration (FDA) and is intended to potentially support the approval of cosibelimab in this indication. As of the March 2022 data cutoff, the objective response rate (ORR) determined by independent central review (ICR) in 31 patients was 54.8% (95% CI: 36.0, 72.7), substantially exceeding a clinically meaningful lower bound of the 95% two-sided confidence interval of 25%.
Based on these positive results, Checkpoint intends to continue discussions with the FDA on the potential addition of locally advanced cSCC as a second indication in the planned Biologics License Application (BLA) targeted for submission later this year. Checkpoint previously reported positive top-line data from a cohort of 78 patients with metastatic cSCC in its pivotal trial of cosibelimab. Cosibelimab (formerly referred to as CK-301) is a potential best-in-class, high affinity, fully-human monoclonal antibody of IgG1 subtype that directly binds to programmed death ligand-1 (PD-L1) and blocks the PD-L1 interaction with the programmed death receptor-1 (PD-1) and B7.1 receptors.
Cosibelimab's primary mechanism of action is based on the inhibition of the interaction between PD-L1 and its receptors PD-1 and B7.1, which removes the suppressive effects of PD-L1 on anti-tumor CD8+ T-cells to restore the cytotoxic T cell response. Cosibelimab is potentially differentiated from the currently marketed PD-1 and PD-L1 antibodies through sustained >99% target tumor occupancy to reactivate an antitumor immune response and the additional benefit of a functional Fc domain capable of inducing antibody-dependent cell-mediated cytotoxicity (ADCC) for potential enhanced efficacy in certain tumor types.
